Thick fog covering most of south east England left flights delayed and cancelled this morning, while others have been hit by problems over the past week. If you've been affected, here's a round-up of your rights.

Poor visibility this morning led to 40 flights being cancelled at London's Heathrow Airport, while across the capital at London City Airport, nearly every early-morning service was either delayed or cancelled (see our Flight Delays guide for your delay and cancellation rights).

This morning's fog problems follow Saturday's major disruption at all airports after difficulties at the Hampshire headquarters of air traffic control company Nats.

And yesterday, an accident at Stansted meant no planes were able to land at the Essex airport for around three hours.

If your flight is cancelled or delayed, you may be able to claim a refund or compensation, or both, depending on the circumstances. These rules only apply to EU flights, which is where the flight departed from an EU airport, regardless of the airline, OR where an EU airline landed at an EU airport.

If you're not on an EU flight, check if similar compensation schemes exist. If they don't, complain to the airline. You should also check if you're covered by your travel insurance.

Cancelled flights

When a flight is cancelled, however long before it was due to take off, and regardless of the cause of the cancellation, you have a right to:

  • Either a refund for the flight that was cancelled.
  • Or an alternative flight to your destination (airlines call this re-routing).

If you choose to be re-routed at the earliest opportunity, airlines also have to provide assistance such as food, phone calls and accommodation where appropriate – even if the cancellation isn't the airline's fault.

Some passengers whose flights are cancelled within 14 days of their journey may also be able to claim additional compensation of between €125 (£105) and €600 (£505) per person, depending on the delay in getting to their destination, the distance travelled, and when exactly they were told of the cancellation.

However, to claim this compensation, the cause of cancellation has to be the airline's fault. Fog and bad weather are classed as "extraordinary circumstances", meaning a claim for compensation is unlikely to be successful.

See our Flight Cancellations guide for more information, as well as details on how to claim compensation.

Delayed flights

If your flight's departure is delayed for more than two hours, then regardless of what caused this delay, your airline may have to look after you until your flight departs, depending on the length of your flight. This means you could be provided with food, drinks, communications, and accommodation if you are delayed overnight.

But to claim compensation for a delayed flight, you need to meet certain criteria.

  • It must have been the airline's fault to claim. The delay had to be under the airline's control. Staffing problems, poor planning, and under-booking all count. Political unrest or bad weather don't.
  • Delays must be over three hours to get compensation. The amount you get is fixed solely on the flight length and delay time. So a 1,000km flight delayed by four hours is €250 (£210) per person, while a 4,000km flight delayed for five hours is €600 (£504) per person.
  • You can go back to 2005. This doesn't just apply to recent flights. If you've been delayed at any time since 2005, you have a right to compensation under EU rules. Though in the UK, it's easier in practice if it's been since 2007.
  • How to claim. Write to the airline stating the details of your delay and asking for the compensation. If it rejects you, depending on where you flew from and the airline you flew with, go to the CAA, the European Consumer Centre, or the regulator in the country you departed from to get a ruling.

For departures delayed by five hours or more, if you decide not to travel, you can also get a refund of your ticket, regardless of what caused the delay.

For full information, including free template letters, see our Flight Delays guide.

Additional reporting by the Press Association.